1. Field of the Invention
The invention concerns a rotor, a gantry and a computed tomography apparatus with a rotor on which components of an acquisition device are mounted.
2. Description of the Prior Art
Computed tomography apparatuses enable the reconstruction of three-dimensional slice or volume images of an examination region for diagnostic purposes. The reconstruction of an image ensues on the basis of projections obtained by irradiating a subject with an x-ray fan mean of an examination region from different projection directions, by rotation of an acquisition device, so that measurement data for parallel projections from an angle range of at least 180 degrees plus the fan beam angle are acquired for reconstruction of an image. To achieve the rotation of the acquisition device, the computed tomography apparatus has a gantry having a stationary frame and a rotor mounted so that it can rotate by means of a rotating bearing device components of the acquisition device are mounted on the rotor. The rotor conventionally has a rotor wall in the form of an annular disc and a retention ring running along its outer periphery for mounting the components of the acquisition device.
To avoid movement artifacts in the reconstructed image that can arise due to patient or organ movements, it is sought to select the time window for acquisition of the projections required for reconstruction to be as small as possible by the use of high rotation speeds. Rotation speeds of 210 R/min are achieved in current computer tomography apparatuses. In the future the rotation speeds will likely be increased to at least 300 R/min.
Due to the high rotation speeds, the connections between the components of the acquisition device (in particular between the x-ray radiator and the detector, and the rotor) are severely mechanically stressed. The components are typically attached to the rotor by spot connections, for example by a bolt connection. High stress values are generated in the region around the connection point due to the centrifugal forces that occur upon rotation. Without additional stabilizing measures in this region, there is a risk that, given an increase of the rotor rotation speed, the connections may be broken and the components thrown from the rotor.